This type of device is routinely designated by the term DAL standing for Warning laser sensor (in French: Détecteur d'Alerte Laser).
Because laser pulses have a very short duration, and also for reasons of photometric balance, it is commonly accepted in the prior art that, in order to achieve satisfactory sensitivities, DAL must include sensors having an output for each element, whether it is a question of mono-element sensors or sensors comprising groups of mono-elements taking the form of linear sensor arrays having one output for each elementary sensor.
Consequently, as is known in the art, such devices have a large overall size because they include optics for collecting the flux for each sensor or linear sensor array.
Another drawback of this type of DAL lies in the fact that even though they may be sensitive to different wavelengths, typically from approximately 1.06 μm to 1.5 μm, they are not able to distinguish between said wavelengths, which can be a major operational problem because the type of threat cannot be identified.
Such DAL including an optical channel for each linear sensor array are described in the prior art. Thus an “off-axis” DAL is described in a paper published by D. Goular et al. entitled “Off-Axis Warning Laser Sensor” in the journal “Proceedings of SPIE, the International Society for Optical Engineering”. As indicated above, this DAL has the drawbacks of a very large overall size and an inability to distinguish the wavelengths of detected laser pulses.